Details: The presentation, "An American Fukushima? Understanding the Risks of an Upstream Dam Failure at the Oconee Nuclear Station," will be delivered by David Lochbaum, the nuclear safety project director of the Union of Concerned Scientists. He will examine what would happen if the Jocasee Dam upstream of the nuclear power plant were to fail and what safety provisions are in place at the site outside of Seneca.

Admission: Free and open to the public

Federal regulators already know a small chance exists that a dam break upstream of the Oconee Nuclear Station could flood the three reactors outside Seneca.

Just what to do about that — and how soon that ought to happen — will be the subject of a public discussion Wednesday hosted by a local chapter of the Sierra Club of South Carolina.

The group has invited nuclear safety expert David Lochbaum of the Union of Concerned Scientists to come to Clemson for a talk dubbed "An American Fukushima? Understanding the Risks of an Upstream Dam Failure at the Oconee Nuclear Station."

The Oconee Nuclear Station is owned by Duke Energy and is one of the largest employers in the Upstate.

Reached at his office this week in Tennessee, Lochbaum said concerns about flooding at Oconee predate the March 2011 disaster at Fukushima, Japan, where a 43-foot wall of sea water inundated backup cooling systems. The reactors there melted down as a result and released radiation into the environment.

"Nuclear plants are fairly robust," Lochbaum said. "You have safety systems and backups to backups. But flood waters can disable much of that. Electric motors don't work well underwater."

The federal Nuclear Regulatory Commission has identified 35 reactors in the United States — about a third of those currently operating here — that are at risk of flood damage, he said.

"Near the top of the list were the three reactors at Oconee," Lochbaum said.

Duke Energy's Preston Gillespie, the site vice president at Oconee, said the Jocassee Dam, built to guarantee water supply to Lake Keowee downstream, was designed with the potential for earthquake damage in mind. Keowee provides cooling waters for the nuclear plant.

With the disaster at Fukushima, Gillespie said, every nuclear plant in the country has reassessed risks. Duke, he said, has already increased the heights of barriers around critical equipment to protect against a range of natural disasters, including floods.

"We had a head start because of work our engineers had done," Preston said.

John Boska, the project manager in the federal Office of Nuclear Reactor Regulation, said Duke has been addressing flood risk at Oconee "for years."

After federal inspectors studied a breach in a flood wall at Oconee in 2006, they conducted an independent study on the likelihood and consequences of a dam failure at Jocassee, A previous study, conducted in 1995, was undertaken by Duke.

"That's when we concluded there was a higher probability than was previously thought," Boska said.

The "breach" that prompted the regulators' closer review was a panel left open so that plant operators could run some cables through. The panel remained open for about two years.

Lochbaum said the NRC ordered Duke in June 2010 to take a number of steps to better protect Oconee from a dam break at Jocassee upstream. Regulators estimated a wall of water as high as 14 feet could hit Oconee, where a flood wall protects against surges of up to five feet.

Gillespie said Duke is already working on improvements and has long-term plans for more.

"The good news is they know what the problems are and have taken some steps," Lochbaum said.

After the disaster at Fukushima, the NRC ordered every nuclear plant in the country to reassess risks from natural disasaters. With Duke already reassessing Oconee, Lochbaum said, these new orders actually had the effect of delaying the deadline for Duke's response.

Under the Nuclear Regulatory Commission's resposne to Fukushima, Duke must submit a flooding hazard report by March 2013, Boska said.

Lochbaum received a degree in nuclear engineering in 1979 from the University of Tennessee and worked in the nuclear power industry for 17 years before going to work for the Union of Concerned Scientists. He had reported a problem at a plant where he was working in eastern Pennsylvania and ultimately took his concerns to the U.S. Congress.

"They put pressure on the NRC, which put pressure on the power company, which ultimately fixed the problem," he said, adding that after speaking out his career was "toast."

He said he went to work for the Union of Concerned Scientists shortly thereafter and has since focused on how commercial power producers and regulators handle hazards, however remote.

NRC spokesman Scott Burnell said his agency can't talk about all the actions Duke is taking to protect the reactors. He said a taller wall to divert a flash flood from Jocassee down the Keowee River basin to Hartwell Lake is among the possibilities — but designing such a structure is complex.

"The long-term effect you want is to keep water away from the plant," Burnell said. "At the same time, if you don't plan that properly, you could divert water somewhere where it does more harm or, depending on whether it's planned properly, the diversion wall could present other issues for the plant."

A dam break at Jocassee is not the only way Oconee could flood, he said, and he cited the possibility of a super storm settling over the area for five days.

"If you put the wall in the wrong place, you could hold water in," he said.